Traditional heater cable controls operate as a linkage between the control panel and the vent door. In such a device, the cable must be able to withstand tensile and compressive loads because the cable is being both pulled and pushed to operate the vent door. The compressive loads require that the cable be somewhat rigid which, in turn, limits the radius of the bends which the cable can undergo during installation procedures, as well as in the final cable positioning. A further disadvantage of these traditional temperature control devices is that they often require adjustments in the length of the cable after installation into the vehicle.
U.S Pat. No. 5,025,711 discloses an integrated temperature and mode selector for a vehicle ventilation system which can be operated by a single actuator. This device discloses a rotatable shaft coupled to two doors for simultaneous rotation with the shaft. The first door determines the temperature of the air flow, and the second door determines the mode of operation, i.e., a heating, cooling or defogger mode.